Right Subwoofer being "sucked in" when Amp is turned on.

eddiemoffett · 27th July 2009, 03:03 AM

I'd appreciate it if anyone can help. I just bought a used Alesis RA-100, and whenever I turn it on, my right subwoofer gets sucked in all the way. It seems like it's getting too much power or something. Any ideas?

Thanks.

Samuel Jayaraj · 27th July 2009, 03:22 AM

It is more likely that the DC offset voltage is relatively high in that channel.

Jan Dupont · 27th July 2009, 03:36 AM

It can only be DC-offset causing this type of action.

SQLGuy · 27th July 2009, 05:14 AM

Hi Eddie,

Just to be clear, in case you're new to this, this is a pretty bad sign. It means the amp is in need of repair and could easily damage speakers it is connected to. Do not use it until it's been repaired. The problem with the amp itself could be as simple as one or two small transistors that are bad, or as complex as the whole output section blown.

Sorry for the bad news.

Paul

DCPreamp · 27th July 2009, 05:37 AM

Is the woofer getting pulled in and it stays in, or does it just pull in and then relaxes back to normal?

If it pulls in and stays, then you have a serious problem.

If it pulls in, then returns to normal, then you may have a minor problem or it may be a fluke with Alesis amps (like a weird bridging turn-on spike only affecting one channel).

Either way, address it and correct it or you could lose your speakers.

Mcurmi · 20th November 2009, 01:35 PM

I have the same problem and i have had a channel blown on the amp and i was not turning on since i was staying in the protect mode. Now i changed 4 transistors and 2 rectifiers and the amp is turning on but the sub woofer is being pulled in and stays in. What else should i check apart from transistors??

By the way my amps's channel was damaged because it was turned on without any heat sink (therefore over heating)

Spiny · 20th November 2009, 03:56 PM

Please disconnect the speakers! Use a meter to measure the offset, there is no need to attach speakers.
Once the source of the problem (driver transistors, Outputs, power supply etc ) has been found then test using a dummy load (8 / 16 ohm heavy duty resistor ) and make sure it is well before attaching your speakers.

27th July 2009, 03:03 AM	#1
eddiemoffett diyAudio Member Join Date: Jul 2009	Right Subwoofer being "sucked in" when Amp is turned on. I'd appreciate it if anyone can help. I just bought a used Alesis RA-100, and whenever I turn it on, my right subwoofer gets sucked in all the way. It seems like it's getting too much power or something. Any ideas? Thanks.

27th July 2009, 03:22 AM	#2
Samuel Jayaraj diyAudio Member Join Date: May 2001 Location: Bangalore, India	It is more likely that the DC offset voltage is relatively high in that channel. __________________ Sam

27th July 2009, 03:36 AM	#3
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	It can only be DC-offset causing this type of action. __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

27th July 2009, 05:37 AM	#5
DCPreamp diyAudio Member Join Date: Jun 2005 Location: Sacramento, CA	Is the woofer getting pulled in and it stays in, or does it just pull in and then relaxes back to normal? If it pulls in and stays, then you have a serious problem. If it pulls in, then returns to normal, then you may have a minor problem or it may be a fluke with Alesis amps (like a weird bridging turn-on spike only affecting one channel). Either way, address it and correct it or you could lose your speakers. __________________ "Believers cling to the myth despite the evidence, reinterpret the myth to suit the evidence, or lie about the evidence to support the myth." "To err is human; to blame errors on external factors is even more so."

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27th July 2009, 05:14 AM	#4
SQLGuy diyAudio Member Join Date: Jan 2009	Hi Eddie, Just to be clear, in case you're new to this, this is a pretty bad sign. It means the amp is in need of repair and could easily damage speakers it is connected to. Do not use it until it's been repaired. The problem with the amp itself could be as simple as one or two small transistors that are bad, or as complex as the whole output section blown. Sorry for the bad news. Paul

20th November 2009, 01:35 PM	#6
Mcurmi diyAudio Member Join Date: Nov 2009	I have the same problem and i have had a channel blown on the amp and i was not turning on since i was staying in the protect mode. Now i changed 4 transistors and 2 rectifiers and the amp is turning on but the sub woofer is being pulled in and stays in. What else should i check apart from transistors?? By the way my amps's channel was damaged because it was turned on without any heat sink (therefore over heating)

20th November 2009, 03:56 PM	#7
Spiny diyAudio Member Join Date: Feb 2008	Please disconnect the speakers! Use a meter to measure the offset, there is no need to attach speakers. Once the source of the problem (driver transistors, Outputs, power supply etc ) has been found then test using a dummy load (8 / 16 ohm heavy duty resistor ) and make sure it is well before attaching your speakers.

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